On Mon, 2002-02-25 at 11:56, Sebastian Kun wrote:
> I've been doing some SPEC SFS97 (http://www.spec.org/osg/sfs97r1/) testing
> for my company. SFS is a benchmark
> for evaluating NFS performance, measuring both throughput (NFS ops/sec), and
> latency (ORT, overall response time). In our case, the benchmark created a
> 50GB fileset, consisting of 2 million files and 65000 directories. During
> the test, approximately 10% of the fileset was accessed (read, write,
> getattr, lookup, etc.).
> I have some questions about some unusual behaviour I've noticed under XFS.
> There seems to be a problem with freeing up memory used for the inode cache.
> During the test run, I periodically checked the amount of free memory using
> the top command:
> Mem: 2063220K av, 2050000K used, 13220K free, 0K shrd, 640K buff 138420K
> There's a lot of memory unaccounted for (even taking into account userspace
> apps). I ran 'cat /proc/slabinfo' which came up with the following entries
> of interest:
> xfs_ili 505795 505848 136 18066 18066
> xfs_inode 1433589 1501336 468 187667 187667
> inode_cache 1188597 1279404 512 182772 182772
> (The format of these entries is [name] [active_obj] [total_obj] [obj_size]
> [active_pages] [total_pages])
> As you can see, the xfs_inode cache takes up over 180,000 pages, or around
> 750MB of memory. The inode_cache takes up another 700MB. Even after doing
> several gigabytes of I/O to another filesystem (reiserfs), the memory used
> by the inode caches was still around 1GB. This memory is only freed when
> the filesystem is unmounted.
> Question 1: Is this behaviour normal for XFS?
> Question 2: Is there any way to limit the amount of memory used by the inode
Well, the xfs inode cache is pretty much controlled via the inode cache,
which is only shrunk if you get into the cache pruning code if you run
short of memory.
I can easily prune out my inode cache without doing unmounts, but my
memory size is a lot smaller than yours.
I presume you do not see this issue with other filesystems?
Steve Lord voice: +1-651-683-3511
Principal Engineer, Filesystem Software email: lord@xxxxxxx